Modify how SignifierInterface is produced so it always sets AccountID on Credentials

---
type: change
message: |-
  Modify how SignifierInterface is produced so it always sets AccountID on Credentials

  Previously it was the responsibility of the caller of the Sign method to set the
  AccountID on the produced Credential, but this didn't really make sense. This
  commit makes it so that all SignifierInterface's produced by Signifier
  implicitly set the AccountID field.

  The solution here is still a bit hacky, and ultimately the real solution will
  probably be to refactor the structore of Credential, so that it doesn't have
  AccountID.
change_hash: ADPuz04GuyxWwjo/0/jc7DcsPMl5rK0osSpaqmUxv818
credentials:
- type: pgp_signature
  pub_key_id: 95C46FA6A41148AC
  body: 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
  account: mediocregopher

cmd/dehub/main.go

@@ -150,7 +150,7 @@ var subCmds = []subCmd{
 			}
 
 			sig := account.Signifiers[0]
-			sigInt, err := sig.Interface()
+			sigInt, err := sig.Interface(*accountID)
 			if err != nil {
 				return fmt.Errorf("could not cast %+v to SignifierInterface: %w", sig, err)
 			}
@@ -160,7 +160,7 @@ var subCmds = []subCmd{
 				return fmt.Errorf("could not construct change commit: %w", err)
 			}
 
-			commit, err = sctx.repo().AccreditCommit(commit, *accountID, sigInt)
+			commit, err = sctx.repo().AccreditCommit(commit, sigInt)
 			if err != nil {
 				return fmt.Errorf("could not accredit commit: %w", err)
 			}

commit.go

@@ -108,8 +108,8 @@ func (c *Commit) UnmarshalText(msg []byte) error {
 }
 
 // AccreditCommit returns the given Commit with an appended Credential provided
-// by the given account and its Signifier.
-func (r *Repo) AccreditCommit(commit Commit, accountID string, sigInt sigcred.SignifierInterface) (Commit, error) {
+// by the given SignifierInterface.
+func (r *Repo) AccreditCommit(commit Commit, sigInt sigcred.SignifierInterface) (Commit, error) {
 	commitInt, err := commit.Interface()
 	if err != nil {
 		return commit, fmt.Errorf("could not cast commit %+v to interface: %w", commit, err)
@@ -124,7 +124,6 @@ func (r *Repo) AccreditCommit(commit Commit, accountID string, sigInt sigcred.Si
 	if err != nil {
 		return commit, fmt.Errorf("could not accreddit change commit: %w", err)
 	}
-	cred.AccountID = accountID
 	commit.Credentials = append(commit.Credentials, cred)
 	return commit, nil
 }

commit_test.go

@@ -21,7 +21,7 @@ func TestConfigChange(t *testing.T) {
 
 	// create a new account and add it to the configuration. That commit should
 	// not be verifiable, though
-	newSig, newPubKeyBody := sigcred.SignifierPGPTmp(h.rand)
+	newSig, newPubKeyBody := sigcred.SignifierPGPTmp("toot", h.rand)
 	h.cfg.Accounts = append(h.cfg.Accounts, Account{
 		ID: "toot",
 		Signifiers: []sigcred.Signifier{{PGPPublicKey: &sigcred.SignifierPGP{

config.go

@@ -70,7 +70,7 @@ func (r *Repo) signifierForCredential(fs fs.FS, cred sigcred.Credential) (sigcre
 	}
 
 	for i, sig := range account.Signifiers {
-		if sigInt, err := sig.Interface(); err != nil {
+		if sigInt, err := sig.Interface(cred.AccountID); err != nil {
 			return nil, fmt.Errorf("error converting signifier index:%d to inteface: %w", i, err)
 		} else if ok, err := sigInt.Signed(fs, cred); err != nil {
 			return nil, fmt.Errorf("error checking if signfier index:%d signed credential: %w", i, err)

repo_test.go

@@ -25,7 +25,7 @@ type harness struct {
 
 func newHarness(t *testing.T) *harness {
 	rand := rand.New(rand.NewSource(0xb4eadb01))
-	sig, pubKeyBody := sigcred.SignifierPGPTmp(rand)
+	sig, pubKeyBody := sigcred.SignifierPGPTmp("root", rand)
 	pubKeyPath := filepath.Join(DehubDir, "root.asc")
 
 	cfg := &Config{
@@ -114,7 +114,7 @@ func (h *harness) changeCommit(msg, accountID string, sig sigcred.SignifierInter
 	}
 
 	if sig != nil {
-		if commit, err = h.repo.AccreditCommit(commit, accountID, sig); err != nil {
+		if commit, err = h.repo.AccreditCommit(commit, sig); err != nil {
 			h.t.Fatalf("failed to accredit commit: %v", err)
 		}
 	}

sigcred/pgp.go

@@ -115,7 +115,7 @@ type pgpPrivKey struct {
 // SignifierPGPTmp returns a direct implementation of the SignifierInterface
 // which uses a random private key generated in memory, as well as an armored
 // version of its public key.
-func SignifierPGPTmp(randReader io.Reader) (SignifierInterface, []byte) {
+func SignifierPGPTmp(accountID string, randReader io.Reader) (SignifierInterface, []byte) {
 	rawPrivKey, err := ecdsa.GenerateKey(elliptic.P521(), randReader)
 	if err != nil {
 		panic(err)
@@ -133,7 +133,11 @@ func SignifierPGPTmp(randReader io.Reader) (SignifierInterface, []byte) {
 	if err != nil {
 		panic(err)
 	}
-	return privKey, pubKeyBody
+
+	return accountSignifier{
+		accountID:          accountID,
+		SignifierInterface: privKey,
+	}, pubKeyBody
 }
 
 func (s pgpPrivKey) Sign(_ fs.FS, data []byte) (Credential, error) {

sigcred/pgp_test.go

@@ -38,7 +38,7 @@ func TestPGPVerification(t *testing.T) {
 			seed := time.Now().UnixNano()
 			t.Logf("seed: %d", seed)
 			rand := rand.New(rand.NewSource(seed))
-			privKey, pubKeyBody := SignifierPGPTmp(rand)
+			privKey, pubKeyBody := SignifierPGPTmp("foo", rand)
 
 			sig, fs := test.init(pubKeyBody)
 			data := make([]byte, rand.Intn(1024))

sigcred/signifier.go

@@ -24,12 +24,16 @@ func (s *Signifier) UnmarshalYAML(unmarshal func(interface{}) error) error {
 
 // Interface returns the SignifierInterface instance encapsulated by this
 // Signifier object.
-func (s Signifier) Interface() (SignifierInterface, error) {
+//
+// accountID is given so as to automatically fill the AccountID field of
+// Credentials returned from Sign, since the underlying implementation doesn't
+// know what account it's signing for.
+func (s Signifier) Interface(accountID string) (SignifierInterface, error) {
 	el, _, err := typeobj.Element(s)
 	if err != nil {
 		return nil, err
 	}
-	return el.(SignifierInterface), nil
+	return accountSignifier{accountID, el.(SignifierInterface)}, nil
 }
 
 // SignifierInterface describes the methods that all Signifiers must implement.
@@ -48,3 +52,20 @@ type SignifierInterface interface {
 	// tree can be used to find the Signifier at a particular snapshot.
 	Verify(fs fs.FS, data []byte, cred Credential) error
 }
+
+// accountSignifier wraps a SignifierInterface to always set the accountID field
+// on Credentials it produces via the Sign method.
+//
+// TODO accountSignifier shouldn't be necessary, it's very ugly. Which indicates
+// that Credential probably shouldn't have AccountID on it, which makes sense.
+// Some refactoring is required here.
+type accountSignifier struct {
+	accountID string
+	SignifierInterface
+}
+
+func (as accountSignifier) Sign(fs fs.FS, data []byte) (Credential, error) {
+	cred, err := as.SignifierInterface.Sign(fs, data)
+	cred.AccountID = as.accountID
+	return cred, err
+}